(a) Field of the Invention
The present invention is related to an improved construction of a mold frame, and more particularly, to one used in a blue light unit (BLU) to weaken the reflection rate of the light emitted from the light guide plate, thus to reduce the interference to the streams of light in the light guide plate while diminishing the phenomenon of ripples.
(b) Description of the Prior Art
Whereas, either direct type or edge-lighting type back light unit may be selected for an LCD applied in information system depending on the requirements of the design. Referring to FIG. 1 of the accompanying drawings for a schematic view of a basic construction of an edge-lighting back light unit, the BLU essentially has a light source 20 disposed in a lampshade 12, and has an end of a light guide plate 30 inserted to the open end of the lampshade 12. Multiple optical films 50 and an LCD panel 60 are provided in sequence on the top of the light guide plate. Streams of light emitted from the light source 20 enter from the end of the light guide plate into the light guide plate 30 and radiate towards the expected surface of the plate to achieve the display results by the LCD panel 60. Wherein, each optical film 50 is generally comprised of a lower diffusion film 51, a brightness enforcement film 52, and an upper diffusion film 51 disposed in sequence on the top of the light guide plate 30 for each optical film 50 to increase the diffusion results of the light source for delivering uniform light.
Furthermore, the entire BLU may be assembled in a mold frame 13 as illustrated in FIG. 2 for achieving the purpose of having the entire assembly secured in place. However, the mold frame is generally made of white material and could easily create interference by having the light reflected to overlap in the direction that streams of the light are advancing due to the way of reflecting the streams of light leaving the light guide plate. The main reason causing the interference is the variations of the level extent in the direction of Z axle of the white mold frame and of the polymerization of molding materials. Those variations cause the reflection ones of the streams of light leaving the light guide plate to become uneven and result in overlapped interference. The interference when displayed on the light emitting surface forms ripples.